Patagonia extends for more than 84,000 km of irregular coasts is an area especially apt to evaluate how historic and contemporary processes influence the distribution and connectivity of shallow marine benthic organisms. The true limpet Nacella magellanica has a wide distribution in this province and represents a suitable model to infer the Quaternary glacial legacy on marine benthic organisms. This species inhabits ice-free rocky ecosystems, has a narrow bathymetric range and consequently should have been severely affected by recurrent glacial cycles during the Quaternary. We performed phylogeographic and demographic analyses of N. magellanica from 14 localities along its distribution in Pacific Patagonia, Atlantic Patagonia, and the Falkland/Malvinas Islands.

Patellogastropoda is an ecologically widely diversified group living on various substrata. Juveniles of Lottia tenuisculpta live on rocks and also on the shell of trochid snails, from which host they are thought to derive some benefit. Generally, selective settlement on suitable habitats is one of the most important factors for increasing its growth and survival rates. However, the cue(s) for settlement to specific substrata have been less studied. To prepare for future investigations of settlement, we conducted experiments using described protocols to find the most efficient methods of artificial fertilisation and laboratory culture for L. tenuisculpta. We conducted all described methods of inducing spawning: thermal shocking; hydrogen peroxide treatment; desiccation; ultraviolet irradiation of seawater; bubbling of air; gamete stripping and alkaline maturing. Dissection of male gonads was the most efficient method of collecting sperm and dropping sperm onto mature females was the best method to stimulate egg release. The early development of L. tenuisculpta is mostly identical to other species of Lottia. The larvae settled at the bottom of containers about 96 hours after fertilisation. Adult shells began to grow at 7–8 days and reached 1 mm in length about 50 days after fertilisation.

We describe the current state of speciation in the species complex of the marine gastropod Patelloida saccharina, using mitochondrial COI, 16S RNA, nuclear histone 3 gene and single-nucleotide polymorphism (SNP) markers from 165 specimens collected from 37 localities across the Japanese archipelago. In total, 28 unique COI haplotypes, 16 16S haplotypes, 11 histone 3 haplotypes and 148 734 SNPs were obtained. Genetic assignments and phylogenetic trees recovered three genetically distinct lineages: P. saccharina saccharina, P. saccharina lanx and an unknown P. sp. from Shionomisaki, Wakayama Prefecture. The divergence between P. saccharina saccharina and P. saccharina lanx was estimated to have occurred around 44 000 years ago—too recent to have accumulated the morphological differences that have confounded taxonomic identification. Continuous gene exchange after an initial split is suggested based on demographic history analyses, which allowed for introgression of the P. saccharina lanx genome and the proliferation of intermediate individuals. Speciation, despite the existence of a contact zone in the Ryukyu Islands, possibly occurred due to the eventual reproductive isolation that followed the initial split with gene flow. Patelloida saccharina saccharina and P. saccharina lanx were strongly supported by our results as two separate species, and a revision of the current taxonomic descriptions based on their phylogeny, demographic history and species distribution is proposed.

We report the diversity, distribution and taxonomy of patellogastropod species from the entire mainland Indian coastline. A total of 77 coastal areas with rocky outcrops in the sandy shoreline, covering the entire mainland Indian coastline, were surveyed seasonally (four times a year) during December 2014 to December 2016. Coastal habitat characteristics and the diversity of all groups of limpets from the intertidal areas were recorded. Specimens were identified by external morphological shell and gill characteristics, by the colour of the foot, mantle fringe and radular characteristics. Ecological aspects like habitat preference were also used to distinguish species. Existing diagnostic characters were amended with newer characteristics emerged in our study. Seven species from two families, Nacellidae and Lottiidae, were found along the mainland Indian coastline. Each species is present with several polymorphic forms with different colour banding patterns. Our study revealed distinct variations in the radular teeth at the genus level, but less differences within genera. Patellogastropod diversity was greater along the west coast of India and only Cellana rota was available throughout the mainland Indian coastline.

Pagurus lanuginosus (De Haan, 1833–1850) and Pagurus maculosus (Komai and Imafuku, 1996) are two closely related species of the genus Pagurus, generally referred to as “right-handed hermit crabs”. Previously thought to be color morphs of the same species, recent studies have itemized their unique features. To investigate the molecular and gene expression evolution that have followed the divergence of these two species, we performed transcriptome sequencing and de novo transcriptome assembly using cephalothorax (head) and pereopod (leg) of the two species. Synonymous and nonsynonymous divergence between the two species was estimated to be 0.0246 and 0.0066, respectively. About 5% of the protein-coding transcripts had signatures of positive selection. The phylogenetic analyses showed that the two species are indeed closely related and diverged about 6.24 million years ago. Comparison of tissue expression showed that head expressions were more conserved, and that more genes were upregulated in the legs of P. maculosus leg; while more pigmentation genes were found to be upregulated in the legs of P. lanuginosus. Genes associated with the extracellular matrix and space, chitin binding and chitin-based larval cuticles were found to have higher expression in the legs of P. maculosus, suggesting the roles in morphological differences. This study sheds light on the evolutionary history of the two species at the molecular level.

The tiny epizoic limpet Lottia tenuisculpta lives on rocky surfaces and shells of the snails Omphalius nigerrimus and Reishia clavigera. The movement patterns of the limpet on host snails was observed during 24 h under controlled laboratory conditions. A specific behaviour, referred to as returning behaviour and reminiscent of homing behaviour, was observed in seven out of 20 individuals, and two out of 15 individuals on O. nigerrimus and R. clavigera, respectively. Rotation behaviour, in which limpets changed the direction of the body by one hundred and eighty degrees without changing the position on host snails, was also observed very frequently (17 out of 20 individuals on O. nigerrimus and 10 out of 15 and R. clavigera). This is the first report of such a behaviour. The potential role of this behaviour in creating home scars is discussed.